1. Field of the Invention
The present invention relates to an aqueous ink composition having curability, and an image forming method of forming an image cured by irradiation of radiation.
2. Description of the Related Art
Recently, an aqueous paint and an aqueous ink has been encouraged based on an increase of demands such as a resource protection, an environmental conservation, and an increase of operation stability.
As the aqueous paint and ink, an ink composition containing water as the main medium and capable of being cured by irradiation of active radiation ray such as ultraviolet rays, that is, an aqueous active radiation curable ink is known. The curable ink can be suitably used for image printing, pre-treatment for providing printability of a recording medium, and post-treatment such as protection and decoration of the printed image. Since the ink composition contains water as the main component, the composition has high safety. Recently, when the aqueous active radiation curable ink has been used in recording using an ink jet method, there is demanded a performance where curing progresses with high sensitivity, and a high quality image can be formed.
However, in the present situation, an aqueous active radiation curable ink which achieves dispersion stability necessary for ink used in an ink jet recording method, and can form a cured film which is excellent in, for example, glossiness, adhesiveness, and water resistance by irradiation of light, has not been provided.
It is known to use various pigment dispersant polymers for increasing performance of the ink used in ink jet recording method. For example, there is disclosed an aqueous ink for ink jet recording using a polymer having a benzene ring which is not directly bonded to the main chain as a pigment dispersant (for example, see Japanese Patent Application Laid-Open (JP-A) No. 2009-84494), in which for example, stability over time or dischargeability is excellent. Moreover, as the aqueous active radiation curable ink, there is disclosed the photo-polymerizable/crosslinkable composition where a benzyl dimethyl ketal type water-soluble photo-initiator is used and styrene/acrylic acid/ethyl acrylate copolymer is used as a dispersant (for example, see JP-A No. 2008-247940), in which curing sensitivity is increased.
However, the conventional aqueous ink for ink jet recording does not contain a compound such as a polymerizable monomer, and an image is not printed by providing a process such as photocuring, and therefore it is hard to say that a printed matter using the ink is sufficient from the viewpoints such as adhesiveness to a recording medium and the water resistance of an image.
Moreover, there is a case where the aforementioned photo-polymerizable/crosslinkable composition has insufficient dispersion stability in the ink, and glossiness of a cured film after photocuring cannot be satisfied.